The invention relates to a filter module with layers of a filter medium, between which there are draining spacer elements, the spacer elements which guide the unfiltered material being sealed relative to the filtrate space.
These filter modules are known in diverse forms, its being common to most of these filter modules that the filter layers are made of flat material, therefore filter cardboard, papers, nonwovens or fabrics.
U.S. Pat. No. 4,347,208 discloses a filter module of filter cells with a core consisting of a plastic draining spacer (inner spacer) on which rests on both sides a filter layer of the filter medium in the form of flat disks. In the center of the filter cell is a filtrate opening. These filter cells must be extrusion coated with a plastic material for sealing on the outer edge. This is complex and expensive because special forms which must be adapted to the geometry of the filter cell must be used for this purpose. The filter cell is sealed relative to the space for the unfiltered material by pressing together the two filter material layers which lie on top of one another in the edge area and by forming a U-shaped plastic element which reaches around the edge area.
Similar filter modules are known from EP 0 285 31 B1, U.S. Pat. Nos. 2,088,199, 3,666,107, 5,607,581 and EP 0 327 394 A2, preferably in addition support tubes being used on which the filter cells are located and held.
EP 0 233 999 likewise discloses one such filter module in which between the filter cells there are in addition so-called outer spacers which keep the filter cells at a distance in order to prevent damage, collapse or swelling of the filter cells. In addition, the radial flow between the filter cells will be improved. The inner and outer spaces are shaped differently so that different tools are needed for production. Extrusion coated filter cells are used in this filter module as well.
Step filters cannot be produced with these known filter arrangements.
The object of the invention is to simplify the filter module known from EP 0 233 999 with respect to structure, and the production of a step filter will also be possible.
This object is achieved with a filter module in which each layer of filter medium consists of a layer of deep bed filter material, the spacer elements consist of draining layers and the draining layers and the filter layers are stacked on top of one another without a gap, the draining layers being sealed on alternating sides to the filtrate/unfiltered material space.
Use of layers both for spacer elements and also for the filter layers offers the possibility of stacking all layers on top of one another without for example supporting tubes being necessary, as is the case in filter cells. In addition, it is possible to stack any filter layers in any sequence.
One major advantage is that it is not necessary to extrusion coat two or more layers by complex processes. The layers are simply stacked on top of one another with their seals, and immediately or later before use are compressed for the ready-to-work state.
The deep bed material has organic and/or inorganic fibrous and/or grainy materials. As the base material for the filter layers celluloses or plastic fibers are used, into which for example kieselguhr, perlites or metal oxides or other filtration-active substances can be introduced. Here the kieselguhrs and perlites are used to enlarge the inner surface and thus to increase the sediment absorption capacity.
The filter layers and the draining filter layers are preferably planar.
Preferably at least two filter layers with different degrees of separation are placed on top of one another, by which thus a step filter can be easily produced. The last filter layer of this filter layer arrangement can be made for example as a disinfection layer.
It is also possible to place at least two filter layers with the same degree of separation on top of one another. This is advantageous especially when they are adsorptively acting filter layers, because then the passage length for the unfiltered material can be increased at will so that the adsorptive action of the filter material can develop better.
According to another embodiment, variously adsorptively acting materials can be worked into the filter layers. This means that different materials can be present in different filter layers or that these different materials can also be combined in one filter layer. These filter layers can also be combined with filter layers which are free of adsorptively acting materials.
Sealing of the draining layers to the filtrate or the unfiltered material is done preferably by suitable sealing elements. These sealing elements which can be provided individually for each layer preferably have the same thickness as the corresponding draining layer.
The filter layers must also preferably have the corresponding sealing elements which point to the filtrate space, in an arrangement of filter layers with different permeability and/or degree of separation the tightest layer, i.e. the layer with the highest degree of separation or the lowest permeability, need not necessarily have a sealing element.
Preferably the sealing elements consist of moldings, for example plastic frames, which are inserted together with the layers to form the filter module.
Depending on the embodiment of the filter module, i.e. the arrangement of filter layers and draining layers, several sealing elements can also be stacked on top of one another when they are joined leakproof to one another. Preferably several adjoining sealing elements can be made in one part; this further simplifies production.
Preferably the sealing elements on their end faces have additional structures which can fit into the adjacent layer in order to increase the contact pressure in particular. These structures can be projections, rings, knobs or the like.
The material for the draining layer can be for example a plastic nonwoven. These materials would be strongly compressed in the structure as claimed in the invention if besides the sealing elements there were not other flow elements on the respectively other passage to the filtrate space or space for the unfiltered material which prevent the draining material from being compressed. For this reason, those flow elements are advantageous which consist of a massive frame which has holes, grooves or other flow openings which are located in the plane of the draining layer.
Preferably the draining layer is made integral with the sealing element and/or flow element. It thus becomes possible to produce cost-favorable components which simply need to be combined and joined with the filter layers.
Preferably the sealing elements and/or flow elements are provided with means for mutual connection. The connection means are also made to be easily detachable so that the module components can be easily separated from one another.
These connection means can comprise clips and catch projections.
The filter module as claimed in the invention offers the advantage that the layers can have any geometries. Round or rectangular layers are preferred.
The layers or the module can have several filtrate/unfiltered material channels which need not be arranged centered.
The production costs of the module as claimed in the invention are much lower than in those modules which are composed of filter cells. Disposal can also be clearly improved. The draining layers need simply be separated from the filter layers. When the layers are connected to one another via clips, for example, these clips need simply be separated and the entire module breaks down into its individual layers. The plastic parts and the filter layers can each be disposed of separately. In contrast to filter cells, which would have to be tediously separated first to dispose of the individual components, major simplification is achieved in the module as claimed in the invention.
Other advantages consist in that the filter modules can be operated in both flow directions, i.e. the filtrate space and space for the unfiltered material can be interchanged. In addition, the filter modules can be backflushed.